import pandas as pd
import matplotlib.pyplot as plt

def simple_plot(station_name, variable_name):
    # Load the CSV file
    df = pd.read_csv(f'{station_name}_data.csv')
    
    # Create a simple line plot
    plt.figure(figsize=(10, 6))
    plt.plot(df[variable_name])
    
    # Add title and labels
    plt.title(f'{variable_name} at {station_name}')
    plt.ylabel(variable_name)
    
    # Show the plot
    plt.show()

# Example usage:
simple_plot('CAMS404', 'pm25')